Description
This invention encompasses an article designed to bleach fabrics in an automatic washing machine over a broad range of washing temperatures. The article comprises a porous receptacle in the form of a pouch which contains a dry granular hypochlorite generating bleaching agent. When this article is placed in the aqueous medium of an automatic washing machine at the beginning of the wash cycle, it will release an aqueous hypochlorite solution into the wash water several minutes after the beginning of the washing cycle.
Bleaching agents can be added to automatic washers in the context of a home laundering operation by the administration of a liquid or powdered bleach at the beginning of the wash cycle, or by addition of a water soluble packet containing bleach. The prior art packets dissolve readily in the aqueous medium of the washer. Administration by either of these two methods results in the instantaneous delivery of bleach into the wash water. Associated with the instantaneous delivery of bleach is the problem of high local concentrations of bleach. This instantaneous delivery results in a maximum concentration of bleach at the beginning of the wash cycle and a decrease in concentration during the wash cycle. Since the bleach is most concentrated at the beginning of the wash cycle, most of its work is performed at the beginning of the wash cycle. The detergent also does most of its work at the beginning of the wash cycle. Having the bleach and the laundry detergent acting at the same time decreases the efficiency of the bleach. Fluorescent whitening agents can be degraded by bleach when in solution. It is therefore advisable to delay release of bleach until fluorescent whitening agents have deposited on the fabrics.
There are several problems associated with administration of bleaches into an automatic washing machine in the context of the home laundry. The first problem is in measuring the proper amount of bleach in the case of the liquid or powdered bleach. The second problem is associated with high local concentrations. These high local concentrations cause fabric and color damage to clothing. A third problem which is encountered with the instantaneous administration of bleach is that which results from the continuous decrease in the concentration of bleach during the washing cycle. Increasing the initial concentration of the bleach to such a degree as to insure effective concentration of the bleach during the entire wash cycle would result in additional fabric and color damage.
Most detergents perform their function during the first 5-10 minutes of washing. Since bleach reacts less with soil suspended in wash water than with soil lodged in fabric, maximum fabric cleaning could be achieved by allowing the detergent to do its job and then adding bleach which would attack dirt remaining in the fabric. Thus maximum efficiency of bleaching agent would be achieved if bleach were to be administered after the laundry detergent had an opportunity to work. Delayed administration could be achieved by manually adding one of the existing bleaching agents to the wash water at approximately five minutes after the beginning of the wash cycle. However, this would be inconvenient and it would not solve the problem of high localized concentrations.
It is an object of this invention to provide an article which can be added at the beginning of the wash cycle which contains a pre-measured amount of bleaching agent and which will provide for the delayed release of bleach. Delayed administration of a bleaching agent maximizes the effectiveness of the bleach. Therefore less bleach is required to give the optimal results. Decreasing the amount of bleach minimizes fabric and color damage.
It is a further object of this invention to provide an article which releases bleach in such a manner as to avoid high localized concentrations of bleach, thus minimizing fabric damage.
U.S. Pat. No. 3,154,495 issued to Robson et. al. discloses a dispensing article which is designed to release a hypochlorite solution at a rate which is controlled by the porosity of the dispensing article. This patent does not teach a delay in the administration of bleach. Further, the dispensing article disclosed in this invention will not delay the administration of bleaching agent for a period of time.
U.S. Pat. No. 3,945,936 to Lucas et. al. discloses a porous dispensing article made of polyurethane which is designed to dispense a peroxygen bleaching agent into an automatic dryer. This patent teaches the use of the tumbling action in the dryer to sift peroxygen bleaching compositions through the pouch and onto damp fabric contained in the dryer.
The article of the present invention operates in an entirely different manner. Bleaching agent is dissolved inside the pouch by wash water flowing through the pouch. Once dissolved, the hypochlorite agent will pass through the pouch and into the wash tub where it then comes in contact with fabrics. The Lucas Patent is limited to peroxide bleaches which are not effective in the present invention since these bleaches will not operate efficiently over the wide range of temperatures encountered in automatic washers in the U.S. Further, this patent teaches a controlled continuous administration of bleach where bleach is released in the first ten to fifteen minutes by a sifting action. In the present invention, bleach is not released until several minutes after the beginning of wash cycle.